This invention concerns engines and more particularly internal combustion piston engines of the two stroke type where an air charge is directed into the combustion chamber defined in part by a piston to be compressed by the piston and fuel mixed in the air is burned to create a power stroke as the piston moves down.
The piston does work as a compressor in compressing the inducted air mass, and this reduces the net power produced by the engine. Supercharging increases the mass of combusted air compressed in the chamber and this increases the engine power output. Supercharging is accomplished by roots blowers, exhaust driven turbines, and other externally driven devices. However, the pistons still act as compressors on the pressurized air introduced into the engine by the supercharger.
The inefficiency of the piston engine operating as a compressor reduces the overall efficiency of the engine, and the superchargers heretofore used have not alleviated this source of inefficiency as supercharged engines still use the pistons as compressors. Such prior superchargers have not approached the efficiency of the trochoidal rotor compressor.
It is the object of the present invention to improve the efficiency of the internal combustion piston engine by providing a more efficient air compressor.
Two stroke engines also are less fuel efficient since some fuel is exhausted because the cylinder is purged with the incoming fuel-air charge. Also, pressurization of the crank case prevents the use of a conventional pressure lubrication system.
Two stroke diesel engines have incorporated a supercharger, with incoming air purging the combustion chamber to alleviate these drawbacks.
However, the compressed air exhausted wastes power, and the blowers used are also inefficient.
The above recited object and others which will become apparent upon a reading of the following specification and claims are achieved by a two stroke hybrid engine in which substantially fully compressed air is introduced into the combustion chamber as the piston approaches top dead center. A trochoidal compressor is coupled to a two stroke piston engine via its crankshaft, so as to produce the highly compressed air, which is then directed into the combustion chambers upon opening of an intake valve or valves. The piston is not substantially relied on to compress the air charge, but rather the very efficient trochoidal rotor compressor takes over this function to significantly improve the engine net power output. Fuel is injected into the compressed air and ignited to generate a power stroke.
In a diesel form of the invention, the air may be compressed sufficiently to ignite the fuel as it is injected.